I'm not a fan of EBB's, let alone chain tensioners. From 2009 I've been riding a steel Cotic Roadrat, it's perfect in all other aspects but cannot compete in weight. It's quite exactly 1,99kg for the frame and 990g for the fork cut, not bad for steel, but there's a lot of weight to save.

You may pretty much be stuck with an EBB if you want to get a carbon fixie. You clearly realize that you have to adjust your rear wheel back and forth with traditional rear-facing slots and a single speed with a straight chain run. That of course moves the rear rotor within the rear disc caliper. Also, the disc caliper posts have to be on the forward side of the seat stay or mounted on the chain stays or you can't get the wheel out. You could choose to change gears in very small movements of the rear wheel by changing chain length and limiting your gears, and might get away with the rotor positioning a bit, but that's a pretty funky way to go about things. You could also use a slack chain, a fixed rear wheel position, and a spring-loaded chain tensioner, which with a rear freewheel (not with a fixed cog) at least takes care of chain tensioning without moving the rear wheel, but does of course create another spot for mud to accumulate. However, the chain tensioner is no more of an issue than a rear derailleur would be in a multi-speed bike anyway. There are some nice chain tensioners out there, or you could even use a carbon road frame with a rear derailleur installed simply as a tensioning device (so that it doesn't actually move laterally to shift gears -- just changes tension depending on the wheel you drop in. This latter is really the simplest solution and allows for a carbon road frame and with a single speed setup without complications. If you want elegant, however, I'd probably stick with steel for now until disc technology gets a bit more advanced. The steel frame makers are coming up with disc caliper mounts that accommodate a single speed with rear slots, but those still look pretty funky -- just look at what All City is doing to their disc single speed Nature Boy this next year. The one exception would be to use Paragon sliding disc stay ends, which constitute a goodly sized piece of titanium or steel but at least give you a quality adjustment in an otherwise carbon frame.

@11.4 - The ENO hub works fine if you know how to set it up correctly. The combo isn't exactly light and the way it works is likely to put someone off if they're not interested in an eccentric bottom bracket...

Depending on your frame/brake setup, it's possible to get away without the adapter, but then you're stuck without 'on the fly' and may as well just run a magic ratio which works well for lots of people.

@11.4 - The ENO hub works fine if you know how to set it up correctly. The combo isn't exactly light and the way it works is likely to put someone off if they're not interested in an eccentric bottom bracket...

Depending on your frame/brake setup, it's possible to get away without the adapter, but then you're stuck without 'on the fly' and may as well just run a magic ratio which works well for lots of people.

I don't get it. The axle is fixed. The hub shell moves to move the cog, which means it moves the disc rotor. Unless the hub moves only enough to keep the rotor within the disc caliper, it doesn't work. Is your solution one that has the rotor move back and forth in the caliper? The only way really to make this work is to position the caliper so it's aligned on a line parallel to the line of hub travel. An ENO hub moves the hub in a circle, but it's a real trick to get the axle in the right position so the rotation doesn't change the disc's position in the rotor. What am I missing? Can you show some photos of exactly how it's done?

Look at the brake adapter in both pictures - the 2 'eyes' allow it to follow an eccentric path just like the hub.

As the rotor moves when the chain is tensioned, the caliper can be adjusted to suit.

You have to remember that this may not be required every time you remove wheel though. You should be moving the wheel back into basically the same position (which you can see in that video as the shifter gets close to 12 o'clock) and if you do that, the caliper should be close enough and won't need adjustment often.

Look at the brake adapter in both pictures - the 2 'eyes' allow it to follow an eccentric path just like the hub.

As the rotor moves when the chain is tensioned, the caliper can be adjusted to suit.

You have to remember that this may not be required every time you remove wheel though. You should be moving the wheel back into basically the same position (which you can see in that video as the shifter gets close to 12 o'clock) and if you do that, the caliper should be close enough and won't need adjustment often.

The prior post only referred to the ENO hub, not to the eccentric adapter. That adapter limits you to 160 or 180 discs? And doesn't work on post mounts? Paragon had some custom mounts that would do the same and potentially with more rigidity. What's the source for that eccentric adapter?

To the OP, is there any reason that it has to be carbon? It seems like at this stage there isn't anything on the market that suits without an 'adaption' of some sort - EBB/hub etc. Having said that, there appear to be heaps of people running open mold frames with EBB converters without issue. There are plenty of posts on MTBR for example.

There have been a few aluminum disc frames but they're either out of production (eg Bianchi Roger), probably not that light (eg Spot Rallye) or not yet in production (Giant have made a few SS TCX's).

Custom titanium would let you choose all of the options you're after and you should still save a bit of weight over your current frame. Have you considered that?

Even just switching to a new fork and keeping your current frame could save you a decent amount of weight.

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